Xe-100 Steam Generator Tubing: First Order Is for Dow's Plant, Not Amazon's

X-energy, Alleima and Doosan Enerbility announced on Nov. 4 the first order for Xe-100 steam generator tubing, a long-lead part for Dow's proposed four-unit plant in Texas, not for the reactors Amazon is funding. Amazon is not a party to the order, and the companies disclosed no quantity, contract value or delivery dates.

The order still matters for Amazon's plan. X-energy's chief executive, Clay Sell, said at the American Nuclear Society's winter meeting in November 2025, as POWER reported, that one customer choosing one technology on three to four sites would bring the design to nth-of-a-kind cost. Tying that to factories moving from reservations to production is our reading, not Sell's words. This is X-energy's first purchase of Xe-100 steam generator tubing, and Doosan, as POWER reported, ties its reserved capacity to Cascade, Amazon's project with Energy Northwest in Washington; X-energy's own release says only "first two commercial projects". Neither Cascade nor Amazon's Indiana project with AEP has an NRC application on file, so the supply chain is now one step ahead of the licensing.

How an Xe-100 Steam Generator Uses Helium Heat

The Xe-100 is a high-temperature gas-cooled reactor. Helium cools a pebble-bed core of TRISO-X fuel, and each module is designed for 200 MWt of heat and 80 MWe of electricity, with an outlet temperature of about 750 C, according to X-energy, which lists these figures on its Xe-100 page. In a pressurized-water reactor, hot reactor water heats the steam generator. In the Xe-100, hot helium does: the gas passes over coiled tubes, the water inside boils, and the steam leaves at up to 565 C, X-energy said. That heat lets one module supply both electricity and industrial process steam. Dow's Seadrift Operations is the site of the proposed Long Mott plant, which is meant to supply power and steam.

X-energy calls the tubing a safety-significant, long-lead component. Alleima, based in Sandviken, Sweden, makes the specialized stainless steel tube, and Doosan bends it into helical coils with its own processes. Alleima says Doosan placed the order with it, and that this is its first tubing order for a helium-cooled small modular reactor (SMR). Alleima opened a new tube mill in Sandviken in June 2026, aimed at conventional nuclear and SMR demand.

What the Doosan Agreements and Amazon Funding Cover

The tubing order rests on three earlier agreements, and each one binds its parties to a different degree. On Aug. 25, 2025, X-energy, Amazon, Korea Hydro & Nuclear Power (KHNP) and Doosan signed a strategic collaboration agreement covering design, supply chain, construction planning and investment. Doosan's chairman called it an MOU. The parties aim to mobilize up to $50 billion of public and private money, and KHNP and Doosan back Amazon and X-energy's goal of more than 5 GW of new US nuclear by 2039. Both figures are aims, not commitments.

On Dec. 18, 2025, X-energy and Doosan signed a binding reservation agreement. Under it, Doosan holds capacity to make the main power system steel for 16 Xe-100 units: reactor pressure vessels, steam generator pressure vessels and other steel parts. X-energy said it committed a significant financial investment to hold the slots, without giving an amount. According to Doosan, as reported by POWER, the 16 units are tied to the four-unit, 320 MWe Long Mott station and the 12-unit Cascade project. Doosan said further agreements would be needed before it starts making the forgings and modules. Amazon is not named as a party. Doosan has also committed to build a new SMR fabrication facility in Changwon, South Korea, that X-energy says is expected to give capacity for approximately 20 Xe-100 reactors a year at full production.

The third piece is fuel. On Aug. 6, 2026, Centrus agreed to supply LEU and HALEU enrichment services from Piketon, Ohio, to X-energy's TRISO-X fuel plant in Oak Ridge, Tennessee, phased to match X-energy's pipeline. The agreement covers part of the initial fuel needs, and no volumes or years were disclosed. Long Mott's first HALEU comes from DOE's HALEU Availability Program.

Amazon's own money goes elsewhere. Amazon led X-energy's 2024 Series C-1 round, which X-energy announced in October 2024 as about $500 million and which Amazon's October 2026 page says "ultimately closed at $700 million", to finish the design and licensing work and the first phase of the TRISO-X plant. In Indiana, it funds the development of 12 Xe-100s, a 960 MW project at the former Breed Generating Station site, and says it would be the plant's first customer. No power contract has been described as signed. None of the releases says whether Indiana's units fall under any component reservation.

How Reactor Component Reservations Differ From Orders

A capacity reservation and a purchase order are different contracts. In December 2025, X-energy and Doosan signed a binding reservation that holds Doosan factory capacity for the main power system steel of 16 Xe-100 units, in exchange for what X-energy calls a significant financial investment (amount not disclosed). It secures a place in the production line, not finished parts; Doosan said follow-up agreements to start manufacturing are expected, as POWER reported.

The Nov. 4 tubing order goes a step further: it buys an actual component, steam generator tubing that Alleima will make and Doosan will bend into helical coils, for the proposed four-unit Long Mott plant. Quantity and value are undisclosed. For Cascade and Indiana, which have no NRC application on file, no source read says a reserved slot has become an order yet.

Where Long Mott, Cascade and Indiana Stand With the NRC

Long Mott is furthest along. X-energy announced on Oct. 30 that the NRC had completed its safety review with a final safety evaluation report. The NRC's independent Advisory Committee on Reactor Safeguards supports issuing a construction permit under Part 50. A construction permit allows building, not operation. As of Nov. 4, the NRC had not announced a permit decision, as Voltgrid's Long Mott coverage and our project file track.

Cascade is still in pre-application. X-energy's chief executive has targeted the construction permit application for the first half of 2027, a slip from end-2026, as our Cascade project file reported. Indiana is at the feasibility stage, with no NRC filing, as described in our Indiana project file.

What the Tubing Order Means for Amazon's Data Centers

For Amazon, the order is a test of supplier readiness, not a change in its power supply. The first Xe-100 steam generator order is for a plant whose power and steam go to Dow. Cascade's first four modules, up to 320 MW that Amazon has the right to buy, depend on factory slots Doosan has reserved. Those slots still need follow-up contracts, and Cascade still needs an NRC permit that has not been applied for. As we argued in our analysis of the NRC review, Long Mott lowers the design risk for every later Xe-100, but not the project risk at Amazon's sites.

There is a comparison for the suppliers. Alleima has made SMR tubing for Doosan before: about 200 km for NuScale, booked in early 2025, its second such order. That was a water-cooled design. Doosan also won NuScale's first reactor vessel module order, as Voltgrid reported. Doosan, which runs an integrated nuclear manufacturing facility in Changwon, per Alleima, now has tubing-related work for two SMR programs, NuScale's and X-energy's. For Amazon, that makes slot timing worth watching.

What to Watch After the Tubing Order

On Nov. 12, X-energy reports third-quarter results, with a call at 8:00 a.m. ET. Watch for the tubing order's size or value, and for any follow-up Doosan manufacturing contract. The NRC's Long Mott construction permit decision is pending, with no date set. Cascade's permit application is targeted for the first half of 2027. For Indiana, the next markers are an owner, an NRC filing and a signed Amazon power contract. None has been announced.